The present disclosure pertains to vitrectomy probes, systems, and methods. More particularly, but not by way of limitation, the present disclosure pertains to vitrectomy probes, systems, and methods utilizing an ovalized tubular cross section and a fluid port contour providing enhanced fluid flow and a guiding surface.
Microsurgical procedures frequently require precision cutting and/or removing of various body tissues. For example, certain ophthalmic surgical procedures require cutting and removing portions of the vitreous humor, a transparent jelly-like material that fills the posterior segment of the eye. The vitreous humor, or vitreous, is composed of numerous microscopic fibrils that are often attached to the retina. Therefore, cutting and removing the vitreous must be done with great care to avoid traction on the retina, the separation of the retina from the choroid, a retinal tear, or, in the worst case, cutting and removal of the retina itself. In particular, delicate operations such as mobile tissue management (e.g. cutting and removal of vitreous near a detached portion of the retina or a retinal tear), vitreous base dissection, and cutting and removal of membranes are particularly difficult.
Microsurgical cutting probes used in posterior segment ophthalmic surgery may include a hollow outer cutting member, a hollow inner cutting member arranged coaxially with and movably disposed within the hollow outer cutting member, a port extending radially through the outer cutting member near the distal end of the outer cutting member, and a port extending radially through the inner cutting member near the distal end of the inner cutting member. Vitreous humor and/or membranes are aspirated into the open port of the outer cutting member and the inner member is actuated to distally extend the inner cutting member. As the inner cutting member extends distally, cutting surfaces on both the inner and outer cutting members cooperate to cut the vitreous and/or membranes, and the cut tissue is then aspirated away through the inner cutting member. Vitreous and/or membranes are then aspirated into the open ports of both the outer and inner cutting members and the inner member is actuated to proximally retract the inner cutting member. The inner and outer cutting members cooperate to again cut vitreous and/or membranes and aspirate the cut tissue away. The actuated extension and retraction of the inner cutting member is repeated at dynamic cycle rates between several tens to several hundred times per second.
These microsurgical cutting probes may compromise traction transmitted to the retina due, for example, to existence of an annular space existing between the outer cutting member and the inner cutting member that can cause incarceration or incomplete shearing of vitreous. In addition, vitreous and/or membranes tend to resist flow through small orifices and lumens such as those in these microsurgical cutting probes. Finally, microsurgical cutting probes' inner cutting member is typically bent near its distal end to bias the distal cutting surface toward the port in the outer cutting member, which provides a flexural side load to facilitate shearing. This can result in the inner cutting member protruding too far out of the port in the outer cutting member as the inner cutting member moves across the outer port, causing irregular high-speed dynamic shearing motion, thus increasing wear of the probe which can lead to incarceration or incomplete shearing of vitreous.